Semiconductor dies are typically formed using a silicon substrate. The substrate may form a carrier or the carrier may be the surface upon which the circuitry is built. Channels are drilled, bored, or etched through the silicon to allow metal contacts at one level in the silicon to be connected to another level in the silicon. The channels are referred to as TSVs (Through-Silicon Vias). In order to make an electrical connection, the vias are lined or filled with a conductive material such as copper or aluminum. The vias are used in a variety of different ways. One way is to connect the circuitry formed on one side of the silicon substrate to external connections on the other side of the silicon substrate. These connections may be for power or for data. In some cases, the circuitry is formed in multiple layers on top of one another within the silicon substrate and vias are used to connect circuits on different layers.
Vias are also used in electronic and micromechanical packaging. Many types of packages have a substrate to which one or more dies are attached. The package substrate has an array of electrical connections to the die on one side. The electrical connections are usually using solder balls or wiring pads. The package substrate also has electrical connections on the other side to make an external contact to a socket, a circuit board, or some other surface. In between the connection arrays, there are one or more routing layers to allow points on the die to connect to the external points. TSVs are also used to connect the different routing layers to each other. TMVs (Through-Mold Vias) are used in a similar way within a package to connect components within the package together that are separated by a molding compound.
Through silicon vias (TSVs) are normally filled with a simple metal (e.g. copper (Cu), tungsten (W), aluminum (Al) etc.). The layer stack within the opening of a typical TSV is first a dielectric, such as silicon oxide (SiO2), to electrically isolate the Si sidewall from the metal fill. A metal diffusion barrier and adhesion layer (e.g. Ti, TiN, Ta, TaN, Ru, WN, etc.) is then used over the dielectric in a TSV or TMV to prevent diffusion of metal ions from the metal fill into the Si substrate and to improve the adhesion of the metal fill in the TSV. Finally, a pure metal fill is deposited by appropriate deposition processes (e.g. electroplating, e-less plating, CVD, sputtering, PVD, etc. or a combination of these techniques)